Software has the luxury of the ability to have rapid change in the hands of users. Web startups are a good example. Even desktop software is a good example. Generally you don't want to apply a strong engineering model to them because the engineering process is costly in time and people. Software on a submarine or for the disk brakes on a car is not a good example because the rapid change can't be cheaply and transparently pushed to the users. Those systems require engineering.
For material products, show me examples where one does not HAVE to get upfront specifications. How would you release early and iterate on an MP3 player or a stove or shoes? The exceptions I can think of are food and landscaping.
Systems (material and software) are engineered because they HAVE to be engineered, not because engineering is inherent in material products and absent in software products. If the system does not require engineering (for safety, cost, risk) then it doesn't look like a good candidate for engineering. Do you engineer your dinner? I don't but NASA does for their astronauts.